The present invention relates to a gas-blast circuit-breaker including at least one stationary and one movable contact member. Additionally, the circuit-breaker includes a compression device, which consists of one actuated compression cylinder that is coupled to the movable contact member and one compression piston that is actuated during the breaking movement oppositely to the compression cylinder. The compression cylinder and the compression piston enclose a compression space. A mechanical limit stop restricts the movement of the compression piston on its side facing away from the compression space and a restoring device pulls the piston rod of the compression piston nearer to the limit stop. The circuit-breaker also includes a device for reinforcing the actuation through the magnetic effect of the breaking current.
In a gas-blast circuit-breaker having a mechanical compression device for the quenching gas including an actuated compression cylinder and a compression piston, the quenching gas is compressed in the compression space and is used after that to blow out the electric arc that is formed when the switch is switched off. In addition to driving the compression cylinder, it is also generally known to drive the compression piston oppositely to the cylinder, in order to more quickly attain a high quenching gas pressure.
German Patent No. 31 41 324 discloses a gas-blast circuit-breaker having a mechanical compression device for the quenching gas, in which the compression piston is actuated in a direction opposite the movement of the compression cylinder, and in which the compression piston consisting of ferromagnetic material is actuated by a magnetic field generated by a coil that is disposed coaxially to the compression piston. The winding density of the coil is variable along its longitudinal axis, so that a uniform gradient field results. During the breaking movement, the coil is traversed by the flow of the breaking current and the compression piston is actuated by the action of magnetic force. German Patent Document No. C-678 029 describes a controlling system for an electric gas switch. This controlling system is supposed to control the gas flow of the quenching gas generated in the switch itself by the action of the electric arc on a material that gives off quenching gas. The control member, namely the sliding cylindrical valve, is adjusted by the magnetic effect of the breaking current. U S. Pat. No. 4,041,263 discloses a gas-blast circuit-breaker, in which a force generated by the magnetic effect of the breaking current acts on the piston of the compression device to reinforce the actuation. For this purpose, the breaking current is carried via a conductor loop that runs in part through the movable piston. This necessitates transmitting the current via sliding contacts. Moreover, the complicated current conduction requires that the movable contact member be coupled to the driving mechanism with insulation.